Relay



s. PEARcE Nov. 19, 1935.

RELAY Filed Jan. 27, 1932 Patented Nov. 19, 1935 UNITED i STATES PATENT 4oFl-ici-z spannen :msm zr, ms, saisi No. saam `xuatically opening the circuit of the starting winding. Fior open motors the centrifugally operated switch has proved to be satisfactory. However. in certain types of refrigerating systems it is desirable to place the motor and compressor withinasealedunitsothatalltherotating 4parts are placed in one enclosed unit, eliminating stuiling boxes and providing simplicity. 'I'his necessitates the operation of the motor within the refrigerant and prevents the satisfac- 'tory use of a centrifugally operated switch in connection with a. motor so situated. For this reason a gravityoperated current relay or electromagnetically operated switch, which closes the starting winding circuit of the motor by the -eifect of the initial inrush of current through the running windings and the electromagnet upon starting the motor, and which opens the starting winding circuit when the current drops and the electromagnet weakens after the motor picks up speed, has been employed for this purpose. 'I'his type of relay however has not been found to be very satisfactory under varying voltage conditions since under conditions of low voltagearelayopensthestartingwindlngtoosoon and under conditions of high voltage the relay opens the starting winding too late and sometimes not at all. When the relay fails to open the starting winding circuit, the starting winding may burn out.

Consequently, the object of my invention includes the provision of an improved starting relay for an induction motor having compensating means for varying line voltage for insuring the opening of the starting winding circuit at the proper time.

A more specific object of the invention is to provide a compensating means actuated by an electromagnet in the starting winding circuit for a gravity operated current relay which is closed by the mittal inrush of curi-mt to the running winding of the motor and opened by gravity as the motor comes up to speed, and the current correspondingly Further objects and advantages of the present invention will be apparent from the following description, reference being had to the aecompanying drawing. wherein a preferred form of the present invention is clearly shown.

lIn the drawing:

Fig. 1 is a diagrammatic illustration of the 10 sealed motor compressor unit having an electric motor of a split phase single phase induction type together with a ditic illustration of the remaining element of a compression refrigeration system; 15

Fig. 2 is a vertical sectional view of my improved relay. and

Fig.3isasectionalviewalongtheline32 of Fig. 2.

Referring to the drawing and more particularly to Fig. l, there is shown diagrammatically for the purposes of illustrating the invention, a sealed motor compressor unit 2li containing a split phase induction motor 2| having a running winding 22, a starting winding 23 and a squirrel 25 cage rotor 24 directly connected to a compressor 2i. The refrigerant compressed by the compressor 26 is forwarded through a supply conduit 28 to a condenser 21 where the refrigerant is condensed and collected in the receiver 20. The refrigerant collected in the receiver 28 is forwarded through the short conduit 29 to an expansion valve 30 of any suitable type located within a cold storage compartment 3|. 'I'he refrigerant, after passing through the expansion valve Il, passes into the evaporator 32 also locatedwitnin the cold storage compartment 3| where the liquid refrigerant vaporizes under reduced pressure and is returned to the compressor through the return conduit 33.

The electrical circuit for the single phase induction motor comprises the electrical conductor 3l which is connected to one end of both the starting winding 23 and the running winding 22 for supplying electrical energy thereto. The other 45 end of the running winding 22 is connected by means of an electric conductor 35 to the solenoid or relay coil 36 which in turn is connected by means of the electrical conductor I1 to the snap acting switch 38 which is operated by means of a 5o thermostatic bulb Il located within the cold storage compartment 3|. The snap acting thermostatically controlled switch 3l is connected by means of the electrical conductor III to the other wire of the single phase alternating current power s6 Cil supply. The other end of the starting winding 23 is connected by means of an electrical con- 'ductor Il to a second solenoid or relay coil I2.

The relay coil I2 is connected through the switch I3 to the electrical conductor J1. The switch I3 is closed by the attraction of the relay coil or electro-magnet 26 to open and close the starting winding circuit at the proper time.

The starting relay is shown in more detail in Figs. 2 and 3. 'Ihe electro-magnet 66, which is connected in the rumiing winding circuit, and the relay coil or electro-magnet I2, which is connected in the starting winding circuit, are bothA mounted upon a platform I6 which is in turn mounted upon a bakelite switch base I6. 'Ihe electro-magnet 36 is provided with a vertically movable core member I1, preferably of soft iron, which is connected at its lower end to a lever I6 which is pivoted at the opposite end of the platform I5 by having its end passing through an aperture I9 and provided with a coil spring 59, a washer 5I, and the cotter pin 52. The movable armature I1 is provided at its lower end with a collar 5I and a felt pad 55 for a cushion. The electro-magnet I2 is provided with a fixed armature 56, also of soft iron, which is provided with a bottom plate 51, also of soft iron.

Between the electro-magnet 26 and I2 there is provided a vertical non-magnetic plate member 58 having feet 39 at its lower end which are mounted upon the platform I5 by means of suitable screws and nuts. The upper end of the vertical plate member 56 is provided with a knife edge 59 which is provided with two upwardly extending projections 60 and 6i at each side. A tilting armature of soft iron 62 is pivotally mounted upon the knife edge 59 at its middle and has its ends extending o ne over the electro-magnet 36 and the other over the electro-magnet I2. The tilting armature 62 is held upon the knife edge 59 by means of a pin 63 which has its lower end held within a recess in the top of the tilting armature 62 and which has its other end held by a leaf spring 6I having its ends forked so as to receive the upstanding projections 66 and 6| of the sheet metal member 58 and which has its ends held down by the cotter pins 65 and 66 which pass through the upstanding projections 60 and 5|.

Mounted upon the switch base I6 is a Z-shaped sheet metal member 68 which supports a stationary Contact 69. A leaf spring 10 supports at one end a movable contact 1| which is adapted to contact with the stationary contact 69 to close the starting winding circuit. The leaf spring 10 is mounted upon the base I6 at its other end by means of the nut and screw 12. The spring is provided with such a tension as to hold the starting winding contacts 69 and 1I closed. 'I'he lever I8 to which the movable amature I1 is connected has a foot or bent down tongue 16 provided with a button 19 which rests upon the flat spring 10 to hold the contacts 69 and 1| separated when the movable armature I1 is in its lowerv or released position. The tilting armature 62 is provided with a set screw 15 at the end over the electro-magnet 36. This set screw is provided for varying the air gap between the movable armature I1 and the tilting armature 62 when the tilting armature 62 is in full line pomtion, as shown in Fig. 2. By reducing the air gap between the movable armature I1 and the tilting armature 62, the electro-magnet 66 is strengthened; conversely as the air gap is increased the electro-magnet 36 is weakened. A sheet metal stop member 16 has its lower end fastened to the platform I5 and its upper end bent inwardly so as to serve as a stop for the upward movement of the one end of the tilting armature 62 so as to prevent too great a clockwise movement of the tilting amature. 5

The operation of the starting relay is as follows: When the thermostatic switch 66 is opened and neither winding is energized, the tilting amature 62 assumes the lfull line position shown in Fig. 2. Likewise, the movable armature I1 is 10 in its lower position, maintaining the starting winding contacts 69 and 1I separated. When the thermostatic switch I6 closes, the current will fiow through the running winding 22 and the electro-magnet I6. 'I'his initial current is far 15 above the normal amount of current consumed i since the motor is stationary and this causes a sumcient pull of the electro-magnet 36 upon the movable armature I1 to raise the movable armature I1 and the lever I6 to allow the flat leaf 20 spring 16 to spring upwardly and to close the starting winding contacts 69 and 1I. The closing of the starting winding contacts 6l and 1I will permit electric current to iiow through the starting winding 2l as well as the electro-magnet 25 I2. By reason of its high resistance, the starting winding 26 will produce a magnetic field acting upon the rotor 2I which is slightly out of phase from that provided by the running winding 22 and as a result there is provided 'a rotating 60 eld which will cause the rotor 2I to rotate and. increase in speed. As the motor increases in speed, the amount of current flowing through the starting and running windings will be reduced so that finally the attraction of the electro-magnet 36 upon the armature I1 will become so weak that the armature I1 will fall or drop out and separate the starting winding contacts 69 and 1I.

The current owing through the starting winding circuit is responsive to the line voltage and In the speed of the motor. For the same motor speed the current through the coil or electromagnet I2 will vary according to the line voltage. Therefore, the pull of the electro-magnet I2 will vary according to the line voltage. 'I'he set screw 15 of the tilting armature 62 is preferably so set as to make the air gap such an amount that the starting relay will operate properly at the lowest line voltage which is to be met in operation. At this lowest line voltage the tilting armature 62 60 will be in the full line position of Fig. 2. However, when higher line voltages occur, the attraction of the electro-magnet I2 upon the tilting armature 62 will be increased, causing the tilting armature 62 to be tilted clockwise a suiilcient 66 amount, which is controlled by the attraction of both the electromagnets, so as to increase the air gap a sufficient amount to cause the electromagnet 36 to be weakened and to permit the movable armature to fall or drop out sooner at a lower speed and in this way give a proper compensation for higher voltage operation. The tilting armature 62 will move to the proper position to properly compensate for line voltages above the minimum for which the starting relay 65 is set. In this way proper starting of the compressor motor is assured. An advantageous feature of this starting relay is that the opening of the starting winding circuit also prevents the ilow of current through the compensating electro- 7o magnet I2, preventing any consumption of the electric energy after tripping the starting switch and also preventing any chattering of the tilting armature 62.

ThusIhave providedastarting relaywhichu properly compensates itself for varying line voltages and which also prevents the use of the electrical energy by the compensating electromagnet after the starting relay has tripped. thus preventing chattering oi' the tilting armature 62 which is then held in full line position by the attraction oi the electro-magnet 36.

While the i'om ci embodiment oi the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. A starting relay switch for an induction motor, including a solenoid having a movable armature, a second solenoid, a set of switch contacts, means connecting said movable amature and one of said switch contacts to open and close said switch contacts, and means controlled by the magnetic attraction of the iirst mentioned and the second solenoid for varying the actuation of the movable amature.

2. A starting relay switch for an induction motor including a ysolenoid having a movable amature with a variable air gap, a second solenoid, a set o! switch contacts, means connecting said movable armature and one of said switch contacts to open and close said switch contacts, and means controlled by the magnetic attraction of said ilrst mentioned and said second solenoids for controlling the air gap of the movable armature.

3. A starting relay switch for an induction motor including a solenoid having a movable amature with a variable air gap,'a second solenoid, a set oi switch contacts, means connecting said movable amature and one of said switch contacts to open and close said switch contacts,

. and means moved by said second solenoid for increasing the air gap oi the movable armature.

4. A starting relay switch for an induction motor including two `solenoids, one oi' said solenoids having a movable amature. a pivoted compensating armature in inductive relation with both of said solenoids, a set oi switch contacts, said movable amature being operatively connected with one of said switch contacts to open and close said switch contacts.

5. A starting relay switch for an induction 5 motor including a solenoid having a stationary armature, a second solenoid having a movable amature, said solenoids being positioned side by side, a tilting compensating armature in inductive relation with both of said solenoids, the power oi said second solenoid being varied by the movement oi said tilting compensating armature, a set of switch contacts, said movable amature being connected to one oi said switch contacts to open and close said switch contacts. l5

6. A starting control means for a single phase induction motor having a. running winding and a starting winding including an electrical circuit for supplying electrical energy to said starting and running windings, a solenoid in series with saidrunning winding, a set of switch contacts in series with said starting winding adapted to be opened and closed to control the iiow of electrical energy to the starting winding, a movable armature for said solenoid, said movable armature being connected to close said switch contacts when attracted by said solenoid and being returned by yielding means to open said switch contacts, and electromagnetic means in series with said starting winding for varying the inherent strength of said solenoid to compensate for varying voltage conditions to cause said switch contacts to be opened at the proper time.

'1. An electromagnetic switch for an electric circuit including a solenoid having a movable armature, a second solenoid, a tilting armature in inductive relation with each of said solenoids, a switch means connected to one of the armatures for controlling the ilow of electric energy through o the electric circuit, said other armature having means for varying the eilective strength of one of the solenoids.

GEORGE CALL PEARCE. 

